- Energy-Transfer-Mediated Photocatalysis by a Bioinspired Organic Perylenephotosensitizer HiBRCP
-
Energy transfer plays a special role in photocatalysis by utilizing the potential energy of the excited state through indirect excitation, in which a photosensitizer determines the thermodynamic feasibility of the reaction. Bioinspired by the energy-transfer ability of natural product cercosporin, here we developed a green and highly efficient organic photosensitizer HiBRCP (hexaisobutyryl reduced cercosporin) through structural modification of cercosporin. After structural manipulation, its triplet energy was greatly improved, and then, it could markedly promote the efficient geometrical isomerization of alkenes from the E-isomer to the Z-isomer. Moreover, it was also effective for energy-transfer-mediated organometallic catalysis, which allowed realization of the cross-coupling of aryl bromides and carboxylic acids through efficient energy transfer from HiBRCP to nickel complexes. Thus, the study on the relationship between structural manipulation and their photophysical properties provided guidance for further modification of cercosporin, which could be applied to more meaningful and challenging energy-transfer reactions.
- Zhang, Yan,Xia, Mingze,Li, Min,Ping, Qian,Yuan, Zhenbo,Liu, Xuanzhong,Yin, Huimin,Huang, Shuping,Rao, Yijian
-
p. 15284 - 15297
(2021/11/01)
-
- Photocatalyst-free visible light promoted: E → Z isomerization of alkenes
-
A simple and green method of visible light driven photocatalytic E to Z isomerization of alkenes has been developed. A variety of (Z)-alkenes can be prepared in the presence of visible light, without any additional photocatalyst. This protocol features photocatalyst-free conditions, which are mild, tolerant, and operationally simple, and is easy to implement.
- Xu, Jianbin,Liu, Na,Lv, Haiping,He, Chixian,Liu, Zining,Shen, Xianfu,Cheng, Feixiang,Fan, Baomin
-
supporting information
p. 2739 - 2743
(2020/06/17)
-
- Photoinitiated carbonyl-metathesis: Deoxygenative reductive olefination of aromatic aldehydes: Via photoredox catalysis
-
Carbonyl-carbonyl olefination, known as McMurry reaction, represents a powerful strategy for the construction of olefins. However, catalytic variants that directly couple two carbonyl groups in a single reaction are less explored. Here, we report a photoredox-catalysis that uses B2pin2 as terminal reductant and oxygen trap allowing for deoxygenative olefination of aromatic aldehydes under mild conditions. This strategy provides access to a diverse range of symmetrical and unsymmetrical alkenes with moderate to high yield (up to 83%) and functional-group tolerance. To follow the reaction pathway, a series of experiments were conducted including radical inhibition, deuterium labelling, fluorescence quenching and cyclic voltammetry. Furthermore, NMR studies and DFT calculations were combined to detect and analyze three active intermediates: a cyclic three-membered anionic species, an α-oxyboryl carbanion and a 1,1-benzyldiboronate ester. Based on these results, we propose a mechanism for the CC bond generation involving a sequential radical borylation, "bora-Brook" rearrangement, B2pin2-mediated deoxygenation and a boron-Wittig process.
- Wang, Shun,Lokesh, Nanjundappa,Hioe, Johnny,Gschwind, Ruth M.,K?nig, Burkhard
-
p. 4580 - 4587
(2019/05/14)
-
- Immobilization and continuous recycling of photoredox catalysts in ionic liquids for applications in batch reactions and flow systems: Catalytic alkene isomerization by using visible light
-
A catalytic (E)- to (Z)-isomerization of olefins using a photoredox catalyst under mild reaction conditions is presented. A variety of (Z)-alkenes can be prepared in the presence of visible light. A new reaction system allows an easy and efficient scale-up, as well as a continuous flow process in which the photocatalyst is immobilized in an ionic liquid and continuously recycled by simple phase separation. Catalytic (E)- to (Z)-isomerizations of olefins under mild conditions can be achieved by use of a photosensitizer and visible light. A new reaction system such as depicted allows an easy and efficient scale-up, as well as continuous flow processes in which the photocatalyst is immobilized in an ionic liquid and continuously recycled by phase separation.
- Fabry, David C.,Ronge, Meria A.,Rueping, Magnus
-
supporting information
p. 5350 - 5354
(2015/03/30)
-
- Convenient and stereoselective synthesis of symmetrical (E)-stilbenes via homocoupling of 1,3-dibenzylbenzotriazolium bromides
-
Using NaH as the base and DMSO as the solvent, a series of symmetric (E)-stilbenes were prepared in good yields via the -homocoupling of 1,3-dibenzylbenzotriazolium bromides at room temperature. Georg Thieme Verlag Stuttgart · New York.
- Xiao, Xiaohui,Lin, Daqin,Tong, Shuitian,Luo, Hong,He, Yinfeng,Mo, Hailan
-
supporting information; experimental part
p. 1731 - 1734
(2011/09/16)
-
- Allenes in asymmetric catalysis: Asymmetric ring opening of meso-epoxides catalyzed by allene-containing phosphine oxides
-
(Chemical Equation Presented) Unsymmetrically substituted allenes (1,2-dienes) are inherently chiral and can be prepared in optically pure form. Nonetheless, to date the allene framework has not been incorporated into ligands for asymmetric catalysis. Since allenes project functionality differently than either tetrahedral carbon or chiral biaryls, they may create complementary chiral environments. This study demonstrates that optically active, C 2-symmetric allene-containing bisphosphine oxides can catalyze the addition of SiCl4 to meso-epoxides with high enantioselectivity. The epoxide opening likely involves generation of a Lewis acidic, cationic (bisphosphine oxide)SiCl3 complex. The fact that high asymmetric induction is observed suggests that allenes may represent a new platform for the development of ligands and catalysts for asymmetric synthesis.
- Pu, Xiaotao,Qi, Xiangbing,Ready, Joseph M.
-
supporting information; experimental part
p. 10364 - 10365
(2009/12/03)
-
- Enantioselective ring-opening reaction of meso-epoxides with ArSH catalyzed by a C2-symmetric chiral bipyridyldiol-titanium complex
-
This study describes a C2-symmetric ligand comprising a central bipyridine-pinene-derived core and two functionalized diphenylmethanol subunits. [8′-(Hydroxy-diphenyl-methyl)-10,10,10′,10′-tetramethy l-[5,5′]bi[6-aza-tricyclo[7.1.1.02,7/s
- Chen, Yi-Jing,Chen, Chinpiao
-
p. 1313 - 1319
(2008/02/09)
-
- Thioaldehyde S-Oxide (Monosubstituted Sulfines) from Thioacylsilane S-Oxides. Synthesis and Fluorine- and Acid-Induced Z/E Isomerization. 2
-
Aromatic and aliphatic, not enethiolizable, thioaldehyde S-oxides (monosubstituted sulfines) are obtained from stereospecific fluorodesilylation of the corresponding thioacylsilane S-oxides with retention of configuration.A detailed investigation on the mechanism of the desilylation, as well as of the acid and fluoride ion induced Z/E interconversion has been performed.
- Barbaro, G.,Battaglia, A.,Giorgianni, P.,Bonini, B. F.,Maccagnani, G.,Zani, P.
-
p. 3744 - 3748
(2007/10/02)
-
- ZEOLITE-CuNaY CATALYZED DECOMPOSITION OF ARYLDIAZOMETHANE
-
Decomposition of aryldiazomethanes is catalyzed by copper ion-exchanged Y-type zeolite to afford cis-1,2-diarylethylenes in high selectivity.The catalytic activity and selectivity are found to be affected by the exchange level of copper ions in zeolite and the solvent used.
- Onaka, Makoto,Kita, Hiroshi,Izumi, Yusuke
-
p. 1895 - 1898
(2007/10/02)
-
- sym-1,2-Diarylethylenes from α-Lithiated Benzylic Sulfones. Catalysis by Elemental Tellurium
-
The stability of α-lithiated alkyl, allyl, and benzyl phenyl sulfones was studied. α-Lithiated benzyl phenyl sulfones were found to give sym-1,2-diarylethylenes slowly when kept in tetrahydrofuran at ambient temperature for several days.The reaction time was significantly reduced if a catalytic amount (18-24percent) of elemental tellurium was present in the reaction.Other chalcogenides were less effective in this respect.The uncatalyzed reaction produced essentially pure trans olefins whereas the tellurium-catalyzed process afforded substantial amounts of cis isomer(usually 15-35percent).Tellurium tetrachloride in chloroform at ambient to reflux temperature was found to be highly effective in promoting cis/trans isomerization of 1,2-diarylethylenes.The involvement of a carbene mechanism or an intermolecular reaction of α-lithiated benzyl phenyl sulfones is considered in a mechanistic discussion.
- Engman, Lars
-
p. 3559 - 3563
(2007/10/02)
-